pulse echo instrumentation Flashcards
what control could you adjust to improve the signal to noise ration on the image? dynamic range frame averaging gray scale map edge enhancement receiver gain
frame averaging
the incoming raw echo signals must be compressed into a smaller dynamic range b/c:
wide DR results in inc display of electronic noise
wide DR does not allow dif. b/w echoes arriving from dif depths
display cannot accommodate wide DR of the incoming signals
existing wide DR significantly slows frame rate
wide DR compromised spatial res
display cannot accommodate wide DR of incoming signals
b/c the DR of the system electronics & display is less than that of the raw echo data, it must be compressed into usable range
what type of imaging results in selective reception of freq that are 2x that of the transmitted freq? color doppler PW tissue doppler m-mode tissue harmonic
tissue harmonics
technique of frame averaging during real time acquisition is designed to: reduce random noise decrease pixel size redistribute gray scale enhance spatial res increase frame rate
reduce random noise frame averaging (persistence) averages data in pixels over successive frames; slight movements of xducer or patient result in slight changes to specle pattern, so frame avg has the effect of smoothing image to reduce speckle
selective reception of echoes generated within the body by nonlinear propogation describes: compound imaging tissue harmonics speckle reduction 3d image tomographic u/s image
tissue harmonic imaging
a type of sonograpic imaging that transmits two pulses of opposite phase in rapid succession so they can be cancelled upon reception: pulse inversion harmonics compound imaging specle reduction imaging tomographic imaging panoramic imaging
pulse inversion harmonics
effective method to filter out the fundamental freq (transmitted freq) and leave only the harmonic freq for display
what can you do to improve the temporal res? increase # of focal zones increase depth increase sector width decrease acoustic scan line density decrease acoustic power output
decrease the acoustic scan line density
which decreases the time required to create the image which results in increased frame rate
duty factor means:
fraction of time xducer is transmitting
fraction of time xducer is receiving
fraction of time b/w transmitted and received pulse
fraction of time b/w transmitted sound pulses
fraction of time required for round trip travel of sound pulse to 1 cm in tissue
fraction of time xducer is transmitting sound
electronic steering is most commonly applied to which real time xducers? annular sequential linear mechanical sector phased segmental linear
phased array
which is the best choice to help demonstrate tissue boundaries that are not perpendicular to sound beam? speckle reducing algorithm spatial compoounding persistence panoramic imaging TGC
spatical compounding
a method in which sound beam is steered in multiple directions by employing time delays
what is a disadvantage of a water path scanner?
reduces axial res
beam width perpendicular to image plane is inc, resulting in poor elevational res
bubbles in fluid can inhibit sound transmission in body
useful only with low freq
fluid path inc the MI
bubbles in fluid can inhibit sound transmission in body
although they reduce reverberation from shallow structures; they require vigorous maintenance to keep the fluid path completely filled at all times if only partially filled; air bubbles become trapped b/w xducer and probe
what scanning mode doesn't rely on principle of echo ranging to determine interface location m-mode transmission PW static b-mode a mode
transmission
what type of focusing is performed by delay circuitry upon reception? dynamic receive focusing elevational focusing transmit focus multizone transmit mech focusing
dynamic receive focusing
when you select compound imaging which artifact is less likely to be observed refraction shadowing enhancement acoustic speckle all of the above
all of the above
what is the typical farm rate for b mode real time imaging 1-9 kHz 10-50 Hz 100-200 MHz 200-300 Hz .05-.9 Hz
10-50 HZ
what is the advantage of using a 3d/4d xducer w/ automated sweep compared to traditional xducer w/ freehand sweep measurement accuracy spatial res contrast res larger field of view greater scanning flexibility
measurement accuracy
whats the purpose of pre amplification of incoming signal
to decreased DR of signal
inc echo voltages before noise is induced through cable
reduce sensitivity to side lobes
reduce acoustic imped mismatch b/w the tissue and xducer
compensate for attenuation of beam w/ depth
inc echo volt. before noise is induced through cable
The wavelength you obtain from an arterial stenosis demonstrates aliasing. if you increase the PRF to eliminate the aliasing, what artifact could be introduced? multipath reflections spectrum mirror image prop speed error range ambiguity refraction
range ambiguity
what system control determines the ant of amplification that occurs in the receiver? gain acoustic power output rectification PRF dynamic range
GAIN
you are imaging a 3d dataset that has anisotropic res. what does this mean?
spatial res is better than temp res
spatial res is = in all dimensions
contrast res is superior to spatial res
unequal res is present b/w imaging planes
elevation res and contrast res are the same
unequal res is present b/w imaging planes
isotropic res= spatial res is = in all dimesnsions
anisotropic res is the opposite
what action would decrease frame rate? inc PRF inc acoustic scan line density decrease sector width decrease number of focal zones decrease image depth
inc aoustic scan line density
temp res is determined by frame rate. as density of acoustic scan line inc lateral res inc but frame rate dec b/c it takes additional time to perform the pulse-listen sequences.
what is the typical frame rate for b-mode real time imaging? 1-9 kHz 10-50 Hz 100-200 MHz 200-300 Hz .05-.9 Hz
10-50 Hz
if you inc the PRF & leave all other controls unchanged what happens? lat res will improve frame rate will inc frame rate will dec axial res will improve freq will inc
frame rate will increase
in the scan converter, interpolation is performed to:
amplify reflected signal in comparison to background noise
dec dynamic range to a level that can be handled by monitor
amplify weak echo signals from deep structures to compensate for beam attenuation
fill in empty pixels that occur b/w acoustic scan lines
inc number of shades of gray in resulting image
fill in empty pixels that occur b/w acoustic scan lines
interpolation is necessary b/c there is not data available for all pixels in the scan converter matrix. as line density dec, more interpolation is needed to fill empty spaces
frame averaging during imaging is designed to: reduce random noise dec pixel size redistribute gray scale enhance spatial res inc frame rate
reduce random noise
aka persistence avgs the data in pixels over successive frames; it smoothes the image or reduces speckle
what can you do to improve temp res? inc number of focal zones inc depth inc sector width dec acoustic scan line density dec acoustic power output
dec acoustic scan line density
this dec the time required to create the image which increases the frame rate
you are manipulating a vol dataset that was previously obtained on your pt. what is the max number of imaging planes that can be obtained ? 1 10 100 1000 there is no limit
there is no limit
vol. datasets can be manipulated to show an infinite number of imaging planes w/ many diff. images
you are imaging a fluid filled structure w/ equidistant horizontal bands appearing in the near field. they have decreasing brightness with depth. what artifact is this? slice thickness side lobes reverberation comet tail ring down
reverberation
what adjustment inc the DUTY FACTOR? inc receiver gain inc output power inc PRF inc scanning time inc TGC
inc PRF
PRF= number of pulses emitted in 1 sec
DF= percentage of time that the u/s is being transmitted
as PRF inc, percentage of time the u/s is “on” inc.
when inc scanning depth, which is automatically dec by the system to avoid range ambiguity? number of focal zones sector width PRF PRP PD
PRF
what artifact is from an array xducer due to energy that propagates from the xducer in a direction diff from the primary beam? grating lobe mirror image reverberation range ambiguity acoustic enhancement
grating lobe
they are the same as side lobes but occur only with array xducers.
what artifact is the result of reverberation? comet tail acoustic speckle beamwidth refraction all of the above
comet tail
common with metallic objects; occurs when sound bounces back and forth multiple times b/w two interfaces
what control can improve signal to noise ratio? dynamic range frame averaging gray scale map edge enhancement receiver gain
frame averaging
the range equation describes the relationship b/w:
acoustic impede of 2 media
side lobe intensity b/w two crystals
round trip pulse travel time & dist to reflector
bandwidth & xducer freq
all of the above
round trip pulse travel time & dist to reflector
what effect will you see if you inc reject level? inc # of shades of gray dec low level echoes dec frame rate dec scanning depth dec amplitude of brightest shade of gray
dec low level echoes
rejection is used to eliminate weak echo signals from display
which display mode is used to calculate dist measurements? a mode b mode m mode b-mode & m-mode all of the above
all of the above
the range equation is used to determine: reflector amplitude reflector freq reflector direction reflector depth reflector size
reflector depth
range equation:
d=1/2 ct
d=depth c=speed of sound in tissue t=round trip travel time
what advantage comes from using tissue harmonics? improved contrast res improved penetration improved temp res improved signal to noise ratio increased bandwidth
improve contrast res
you inc imaging depth and scan line density. what does this result in? reduced contrast res reduced temp res improved axial res reduced lat res all of the above
reduced temp res
what is not a function of the receiver: amplification rf to video conversion demodulation dynamic aperture compression
dynamic aperture
it occurs in beam former and pulser
what mode does not rely on echo ranging to determine interface location? mmode PW static b mode transmission b mode
transmission
number of images displayed per second in real time imaging: PRF PRP frame rate PD pulse length
frame rate
what physical concept allows us to determine location of an interface by measuring the elapsed time b/w transmitted pulse u/s wave and detected echo? huygens principle shells law doppler effect echo ranging none of the above
echo ranging
what technique would be most likely to produce grating lobes? tomographic u/s imaging 3d imaging beam steering speckle reduction imaging tissue harmonic imaging
beam steering
using a xducer that produces a beam w/ very wide slice thickness. what problem might you encounter?
decreased penetration
partial volume artifact
increased near field reverberations in fluid structures
side lobes
decreased frame rate
partial volume artifact
aka slick thickness artifact
what system function is limited by the speed of sound in tissue? demodulation voltage amplitude PRF rectification TGC
PRF
which of the following describes an analog signal?
discrete values
fixed steps b/w values
levels are determined by bits
no analog signals exist in modern instruments
continuous variation of the signal is possible
continuous variation of the signal is possible
what is an advantage of a water path scanner? penetration inc temp res is improved near field reverberations reduced axial res improved slice thickness reduced
near field reverberations are reduced
performing a 3d sonogram and volume rate is 8 Hz what does this mean?
number of volumes displayed per sec
number of transmitted sound pulses per sec
number of received pulses per min
number of frames per vol
number of frames per sec
number of volumes displayed per sec
what component of the u/s system converts electric energy provided by pulser into acoustic pulses transmitted into patient? transducer receiver scan converter memory display
transducer
what is the main advantage of having a thin slice over image plane? imrpoved frame rate better axial res dec vol avg larger field of view greater penetration
decreased volume averaging
what effect will you detect in the image if you inc the threshold? inc image brightness dec image brightness inc appearance of strong echo signals dec appearance of weak echo signals dec appearance of strong echo signals
dec appearance of weak echo signals
which of the following helps improve lateral res in b-mode? inc bandwidth focusing with an acoustic lens inc aperture inc dynamic range beam steering
inc aperture
you obtain 3d sweep in axial plane are are viewing it in multi planar display. what orthogonal planes are displayed? transverse and coronal transverse and sagittal oblique planes at 90 degrees coronal and sagittal oblique planes at 60 degrees
coronal and sagittal
which of the following helps to improve the elevation res in b mode? inc transmit power focusing with acoustic lens inc bandwidth inc dynamic range beam steering
focusing with acoustic lens
which artifact commonly results in echoes filling lumen of small vessels? refraction mirror image partial volume range ambiguity multipath
partial volume
which artifact results in axial and lateral displacement of a reflector? multipath reflections refraction side lobe partial volume enhancement
multipath
what type of res is determined by number of pixels in scan converter? spatial temporal contrast elevational all of the above
spatial
number of pixels inc, spatial res improves.
which artifact is related to beam attenuation comet tail enhancement aliasing reverberation side lobe
enhancement
enhancement occurs distal to a structure that has less attenuation of the sound beam compared to surrounding tissue
improve border definition by ? use lower line density use spatial compound imaging use 2d array transducer apply speckle reduction algorithm use frame avg
use spatial compound imaging
propagation speed error results in: improper axial pos of echo improper lateral pos of echo shadowing behind echo enhancement behind echo none of the above
improper axial pos of echo
you are observing sonographic artifact ased on interference patterns of scattered echoes: mirror acoustic speckle grating lobe comet tail refraction
acoustic speckle
complete destructive interference of echo reflections will affect the display in the following way: white pixel dark gray pixel black pixel light gray pixel none of the above
black pixel
inc both imaging depth and scan line density results in: reduced contrast res improved axial res reduced temp res reduced lateral res all of the above
reduced temporal res
greater imaging depth and scan line density decreased the frame rate; axial and contrast res are not affected; inc scan line density will improve lateral res
inc number of acoustic scan lines in one frame improves: lateral res temporal res axial res elevational res contrast res
lateral res
number of lines in frame inc, distance b/w lines decreases; reducing the dist improves lateral res
what component is necessary for real time b mode scanner but not present in a mode? scan converter clock transmitter transducer receiver
scan converter
which is the best to demonstrate tissue boundaries that are not perpendicular to sound beam? speckle reducing algorithm persistence spatial compound panoramic imaging tgc
spatial compound
method which sound beam is steering in multiple directions by employing time delays
